Primary prophylaxis in children with severe haemophilia A and B-Implementation over the last 20 years as illustrated in real-world data in the PedNet cohorts.

INTRODUCTION: The prophylactic regimen in children with severe haemophilia is suggested in various publications and guidelines. Few data exist on its implementation in clinical practice. AIM: To investigate the implementation of primary prophylaxis based on real-life data from PedNet during the last 20 years. METHODS: All children from the PedNet cohort (n = 1260) with severe haemophilia A (SHA) or severe haemophilia B (SHB), FVIII/IX < .01 IU/mL, born between 2000 and 2009 (Cohort I; SHA n = 662; SHB n = 88) and 2010-2019 (Cohort II; SHA n = 598; SHB n = 94) were included. RESULTS: In SHA, the median age at start of prophylaxis was 17.3 months (IQR; 12.5-26.1) in Cohort I which decreased to 13.1 months (IQR; 10.4-19.1) in Cohort II (p < .000). "Once-a-week" prophylaxis at start increased from 49% to 68% (SHA) and 38% to 70% (SHB). FVIII doses were reduced from median 43.5 (IQR; 34.6-49.0) to 30.9 IU/kg (IQR; 26.3-46.3), while dosing with FIX did not change. After 2010 approximately 60% of the patients with SHA and SHB started prophylaxis before any joint bleed. The number of CVADs needed in both cohorts was around 30%. Incidences of inhibitors were unchanged: SHA (∼31%) and SHB (∼10%). Sporadic cases were diagnosed significantly later (median 8.3 months; IQR; 3.7-11.9) and they had more joint bleeds before start of prophylaxis. CONCLUSION: Primary prophylaxis nowadays starts at an earlier age: before any joint bleed (60% of patients with SHA and SHB). Approximately 70% started on a once-weekly schedule with significantly reduced doses in SHA but unchanged in SHB.

Inhibitor development in previously untreated patients with severe haemophilia: A comparison of included patients and outcomes between a clinical study and a registry-based study.

AIM: The aim of this study was to investigate whether a disease registry could serve as a suitable alternative to clinical studies to investigate safety of orphan drugs in children. METHODS: We used individual patient data from previously untreated patients (PUPs) with severe haemophilia A from the factor VIII (rAHF-PFM)-clinical study and the PedNet registry. The primary outcome was the patient characteristics at entry and the difference in inhibitor development between the clinical study and the registry-based study at 50 exposure days. RESULTS: Clinical study patients more often had a positive family history of inhibitors (31% vs 10%) and a high-risk F8 genotype (82% vs 63%). In the clinical study 41/55 (75%) and in the registry-based study 162/168 (96%) patients reached 50 exposure days. Inhibitors developed in 16 of the 41 patients in the clinical study (39%) vs 44 of the 162 patients in the registry-based study (27%); seven patients (7%) vs 28 patients (17%) had high-titre inhibitors. The risk of developing an inhibitor during the first 50 exposure days was similar (HR 1.04; 95% CI 0.56-1.94), when adjusted for family history of inhibitors, F8 gene mutation and intensive treatment at first exposure. CONCLUSION: In the registry-based study, patient numbers and completeness of follow-up were higher. The risk of developing an inhibitor to a single product was comparable. Although the sample size of this study was too small to conclude on differences in high- or low-titre inhibitors, this suggests that a registry could serve as a more suitable source for evaluation of high-titre inhibitors in the setting of factor VIII deficiency.

Clinical trials and registries in haemophilia: Opponents or collaborators? Comparison of PUP data derived from different data sources.

INTRODUCTION: The "Guideline on the clinical investigation of recombinant and human plasma-derived factor VIII products" (ClinGL) provides the requirements for the performing of clinical trials (CTs) for marketing authorization in Europe. The number of eligible previously untreated patients (PUPs) for CTs might be difficult to meet because of the concurrent development of FVIII concentrates, and additional data sources must be explored. AIM: The extent to which CTs and the PedNet registry met relevant parameters, identified in the ClinGL, as well as inhibitor incidences were investigated in patients from both sources. METHODS: Anonymized data of eight CTs in 369 PUPs performed from 1987 to 2009 were compared with each other and with 632 PUPs (born 2000-2009) from PedNet. RESULTS: Clinical trials in PUPs performed for marketing authorization were too heterogeneous in their investigated parameters; therefore, a comparison of single factor concentrates was not possible. Data collection in PedNet met relevant parameters required for PUPs in accordance with the ClinGL. The overall inhibitor incidences were comparable (CT = 30.9% vs PedNet = 30.6%) when only severe haemophilia A (HA) patients from both data sources were considered. CONCLUSIONS: Previously performed CTs in PUPs were divergent, which prevented a direct comparison of outcomes. However, this study demonstrated that data from CTs and carefully designed registries may complement each other in the establishing of sufficient safety information for single products to improve clinical insights and support regulatory decisions.

First-year results of an expanded humanitarian aid programme for haemophilia in resource-constrained countries.

INTRODUCTION: The gaps in haemophilia treatment around the world are enormous; approximately 60% of an estimated 475 000 individuals are not identified. Of the 187 000 diagnosed, 30% (57 000) access clotting factor replacement therapy. Since 1996, humanitarian aid distributed by the World Federation of Hemophilia (WFH) has played a minor, yet vital role providing life-saving clotting factor to countries in emergency situations. Donated amounts have been small and sporadic, often salvaging short-dated products, providing little opportunity to leverage donations with governments. In 2015, a prospective donation programme of 100 million I.U. per year of extended half-life factor VIII and IX over 10 years was established, necessitating the development of new logistics and training programmes by WFH. AIM: To measure the impact of a greatly expanded haemophilia humanitarian aid program. MATERIALS AND METHODS: In 2016, the first full year of the expanded programme, WFH, distributed products to 58 countries with factor VIII usage <1 I.U. per capita, a level incompatible with long-term survival and far below the 4 I.U. FVIII per capita minimum established in Europe. RESULTS: The scope of the programme and utilization data for 2016 indicate primarily use for acute bleeding, orthopaedic and emergency surgeries. Compared to 2014, 2016 data showed substantial increases in patients served (5.9-fold, from 2119 to 14 579), surgeries performed (37-fold) and bleeds treated (6.9-fold). Patients on prophylaxis rose from 0 to 852, including 458 children under 10 years old. DISCUSSION: The expanded humanitarian aid programme impacts an estimated 10% of individuals with haemophilia previously unable to access treatment. CONCLUSION: This programme represents an unprecedented public-private partnership to deliver medicines to individuals with no access. Further, the programme offers the prospective opportunity to engage governments to take more responsiblity for increasing training, medical management, and product supply in 58 resource constrained countries.

Vaccinations are not associated with inhibitor development in boys with severe haemophilia A.

BACKGROUND: Inhibitor development in previously untreated patients (PUPs) with severe haemophilia A is a multifactorial event. It is unknown whether paediatric vaccinations given in close proximity to factor VIII (FVIII) are associated with inhibitor development. OBJECTIVE: To assess whether paediatric vaccinations in close proximity to FVIII within the first 75 exposure days (EDs) are associated with inhibitor development in PUPs with severe haemophilia A. METHODS: We included 375 PUPs with severe haemophilia A (<0.01 IU/mL) from the PedNet Registry who had received vaccinations between the first and 75th ED or inhibitor development. Inhibitor risk was compared between patients who did and who did not receive vaccinations within 24, 72 or 120 hours of FVIII infusion. Unadjusted and adjusted hazard ratios were calculated for any or repeated vaccinations in close proximity to FVIII, using Cox regression. RESULTS: Inhibitor development occurred in 77 of 375 patients (20.5%). Overall inhibitor development appeared similar or lower in patients receiving vaccinations in close proximity to FVIII as compared to patients receiving vaccinations without FVIII: for 24 hours, this was 19.2% and 21.4% (P = .186), for 72 hours, 16.4% and 27.3% (P = .023) and for 120 hours, 18.3% and 25.0% (P = .085), respectively. CONCLUSION: We found no association between vaccinations given in close proximity to FVIII exposure within the first 75 EDs and inhibitor development. Our data do not support avoiding administration of FVIII at time of routine vaccinations.

Molecular-integrated risk profile to determine adjuvant radiotherapy in endometrial cancer: Evaluation of the pilot phase of the PORTEC-4a trial.

OBJECTIVE: The Post-Operative Radiation Therapy in Endometrial Carcinoma (PORTEC)-4a trial is a randomized trial for women with high-intermediate risk endometrial cancer (EC), comparing individualized adjuvant treatment based on a molecular-integrated risk profile to standard adjuvant treatment; vaginal brachytherapy. To evaluate patient acceptability and pathology logistics of determining the risk profile, a pilot phase was included in the study. METHODS: PORTEC-4a is ongoing and the first 50 patients enrolled were included in the pilot phase. Primary endpoints of the pilot phase were patient acceptance, evaluated by analyzing the screening logs of the participating centers, and logistical feasibility of determination of the risk profile within 2 weeks, evaluated by analyzing the pathology database. RESULTS: In the first year, 145 eligible women were informed about the trial at 13 centers, of whom 50 (35%) provided informed consent. Patient accrual ranged from 0 to 57% per center. Most common reasons for not participating were: not willing to participate in any trial (43.2%) and not willing to risk receiving no adjuvant treatment (32.6%). Analysis of the pathology database showed an average time between randomization and determination of the molecular-integrated risk profile of 10.2 days (1-23 days). In 5 of the 32 patients (15.6%), pathology review took >2 weeks. CONCLUSIONS: The PORTEC-4a trial design was proven feasible with a satisfactory patient acceptance rate and an optimized workflow of the determination of the molecular-integrated risk profile. PORTEC-4a is the first randomized trial to investigate use of a molecular-integrated risk profile to determine adjuvant treatment in EC.

A randomised, phase II study of repeated rhenium-188-HEDP combined with docetaxel and prednisone versus docetaxel and prednisone alone in castration-resistant prostate cancer (CRPC) metastatic to bone; the Taxium II trial.

BACKGROUND: Rhenium-188-HEDP is a beta-emitting radiopharmaceutical used for palliation of metastatic bone pain. We investigated whether the addition of rhenium-188-HEDP to docetaxel/prednisone improved efficacy of chemotherapy in patients with CRPC. METHODS: Patients with progressive CRPC and osteoblastic bone metastases were randomised for first-line docetaxel 75 mg/m2 3-weekly plus prednisone with or without 2 injections of rhenium-188-HEDP after the third (40 MBq/kg) and after the sixth (20 MBq/kg) cycle of docetaxel. Primary endpoint was progression-free survival (PFS), defined as either PSA, radiographic or clinical progression. Patients were stratified by extent of bone metastases and hospital. RESULTS: Forty-two patients were randomised for standard treatment and 46 patients for combination therapy. Median number of cycles of docetaxel was 9 in the control group and 8 in the experimental group. Median follow-up was 18.4 months. Two patients from the experimental group did not start treatment after randomisation. In the intention to treat analysis no differences in PFS, survival and PSA became apparent between the two groups. In an exploratory per-protocol analysis median overall survival was significantly longer in the experimental group (33.8 months (95%CI 31.75-35.85)) than in the control group (21.0 months (95%CI 13.61-28.39); p 0.012). Also median PFS in patients with a baseline phosphatase >220U/L was significantly better with combination treatment (9.0 months (95%CI 3.92-14.08) versus 6.2 months (95%CI 3.08-9.32); log rank p 0.005). As expected, thrombocytopenia (grade I/II) was reported more frequently in the experimental group (25% versus 0%). CONCLUSION: Combined treatment with rhenium-188-HEDP and docetaxel did not prolong PFS in patients with CRPC. The observed survival benefit in the per-protocol analysis warrants further studies in the combined treatment of chemotherapy and radiopharmaceuticals.

Investigating the heterogeneity of alkylating agents' efficacy and toxicity between sexes: A systematic review and meta-analysis of randomized trials comparing cyclophosphamide and ifosfamide (MAIAGE study).

BACKGROUND: A marginal interaction between sex and the type of alkylating agent was observed for event-free survival in the Euro-EWING99-R1 randomized controlled trial (RCT) comparing cyclophosphamide and ifosfamide in Ewing sarcoma. To further evaluate this interaction, we performed an individual patient data meta-analysis of RCTs assessing cyclophosphamide versus ifosfamide in any type of cancer. METHODS: A literature search produced two more eligible RCTs (EICESS92 and IRS-IV). The endpoints were progression-free survival (PFS, main endpoint) and overall survival (OS). The hazard ratios (HRs) of the treatment-by-sex interaction and their 95% confidence interval (95% CI) were assessed using stratified multivariable Cox models. Heterogeneity of the interaction across age categories and trials was explored. We also assessed this interaction for severe acute toxicity using logistic models. RESULTS: The meta-analysis comprised 1,528 pediatric and young adult sarcoma patients from three RCTs: Euro-EWING99-R1 (n = 856), EICESS92 (n = 155), and IRS-IV (n = 517). There were 224 PFS events in Euro-EWING99-R1 and 200 in the validation set (EICESS92 + IRS-IV), and 171 and 154 deaths in each dataset, respectively. The estimated treatment-by-sex interaction for PFS in Euro-EWING99-R1 (HR = 1.73, 95% CI = 1.00-3.00) was not replicated in the validation set (HR = 0.97, 95% CI = 0.55-1.72), without heterogeneity across trials (P = 0.62). In the pooled analysis, the treatment-by-sex interaction was not significant (HR = 1.31, 95% CI = 0.89-1.95, P = 0.17), without heterogeneity across age categories (P = 0.88) and trials (P = 0.36). Similar results were observed for OS. No significant treatment-by-sex interaction was observed for leucopenia/neutropenia (P = 0.45), infection (P = 0.64), or renal toxicity (P = 0.20). CONCLUSION: Our meta-analysis did not confirm the hypothesis of a treatment-by-sex interaction on efficacy or toxicity outcomes.

Registries supporting new drug applications.

PURPOSE: Knowledge of the benefits and risks of new drugs is incomplete at the time of marketing approval. Registries offer the possibility for additional, post-approval, data collection. For all new drugs, which were approved in the European Union between 2007 and 2010, we reviewed the frequency, the type, and the reason for requiring a registry. METHODS: The European Public Assessment Reports, published on the website of the European Medicine Agency, were reviewed for drugs approved by the Committee for Medicinal Products for Human Use. We searched for key characteristics of these drugs, including therapeutic area (ATC1 level), level of innovation (the score is an algorithm based on availability of treatment and therapeutic effect), and procedural characteristics. In addition, we identified if these registries were defined by disease (disease registry) or exposure to a single drug (drug registry). RESULTS: Out of 116 new drugs approved in the predefined period, for 43 (37%), 1 to 6 registry studies were identified, with a total of 73 registries. Of these 46 were disease registries and 27 (single) drug registries. For 9 drugs, the registry was a specific obligation imposed by the regulators. The level of innovation and the orphan status of the drugs were determinants positively predicting post-approval registries (OR 10.3 [95% CI 1.0-103.9] and OR 2.8 [95% CI 1.0-7.5], respectively). CONCLUSIONS: The majority of registries required by regulators are existing disease registries. Registries are an important and frequently used tool for post-approval data collection for orphan and innovative drugs.

Effect of Antibiotic Prophylaxis on Surgical Site Infections Following Removal of Orthopedic Implants Used for Treatment of Foot, Ankle, and Lower Leg Fractures: A Randomized Clinical Trial.

Importance: Following clean (class I, not contaminated) surgical procedures, the rate of surgical site infection (SSI) should be less than approximately 2%. However, an infection rate of 12.2% has been reported following removal of orthopedic implants used for treatment of fractures below the knee. Objective: To evaluate the effect of a single dose of preoperative antibiotic prophylaxis on the incidence of SSIs following removal of orthopedic implants used for treatment of fractures below the knee. Design, Setting, and Participants: Multicenter, double-blind, randomized clinical trial including 500 patients aged 18 to 75 years with previous surgical treatment for fractures below the knee who were undergoing removal of orthopedic implants from 19 hospitals (17 teaching and 2 academic) in the Netherlands (November 2014-September 2016), with a follow-up of 6 months (final follow-up, March 28, 2017). Exclusion criteria were an active infection or fistula, antibiotic treatment, reimplantation of osteosynthesis material in the same session, allergy for cephalosporins, known kidney disease, immunosuppressant use, or pregnancy. Interventions: A single preoperative intravenous dose of 1000 mg of cefazolin (cefazolin group, n = 228) or sodium chloride (0.9%; saline group, n = 242). Main Outcomes and Measures: Primary outcome was SSI within 30 days as measured by the criteria from the US Centers for Disease Control and Prevention. Secondary outcome measures were functional outcome, health-related quality of life, and patient satisfaction. Results: Among 477 randomized patients (mean age, 44 years [SD, 15]; women, 274 [57%]; median time from orthopedic implant placement, 11 months [interquartile range, 7-16]), 470 patients completed the study. Sixty-six patients developed an SSI (14.0%): 30 patients (13.2%) in the cefazolin group vs 36 in the saline group (14.9%) (absolute risk difference, -1.7 [95% CI, -8.0 to 4.6], P = .60). Conclusions and Relevance: Among patients undergoing surgery for removal of orthopedic implants used for treatment of fractures below the knee, a single preoperative dose of intravenous cefazolin compared with saline did not reduce the risk of surgical site infection within 30 days following implant removal. Trial Registration: clinicaltrials.gov Identifier: NCT02225821.

Factor VIII products and inhibitor development in severe hemophilia A.

BACKGROUND: For previously untreated children with severe hemophilia A, it is unclear whether the type of factor VIII product administered and switching among products are associated with the development of clinically relevant inhibitory antibodies (inhibitor development). METHODS: We evaluated 574 consecutive patients with severe hemophilia A (factor VIII activity, <0.01 IU per milliliter) who were born between 2000 and 2010 and collected data on all clotting-factor administration for up to 75 exposure days. The primary outcome was inhibitor development, which was defined as at least two positive inhibitor tests with decreased in vivo recovery of factor VIII levels. RESULTS: Inhibitory antibodies developed in 177 of the 574 children (cumulative incidence, 32.4%); 116 patients had a high-titer inhibitory antibody, defined as a peak titer of at least 5 Bethesda units per milliliter (cumulative incidence, 22.4%). Plasma-derived products conferred a risk of inhibitor development that was similar to the risk with recombinant products (adjusted hazard ratio as compared with recombinant products, 0.96; 95% confidence interval [CI], 0.62 to 1.49). As compared with third-generation full-length recombinant products (derived from the full-length complementary DNA sequence of human factor VIII), second-generation full-length products were associated with an increased risk of inhibitor development (adjusted hazard ratio, 1.60; 95% CI, 1.08 to 2.37). The content of von Willebrand factor in the products and switching among products were not associated with the risk of inhibitor development. CONCLUSIONS: Recombinant and plasma-derived factor VIII products conferred similar risks of inhibitor development, and the content of von Willebrand factor in the products and switching among products were not associated with the risk of inhibitor development. Second-generation full-length recombinant products were associated with an increased risk, as compared with third-generation products. (Funded by Bayer Healthcare and Baxter BioScience.).

Enzalutamide as a Fourth- or Fifth-Line Treatment Option for Metastatic Castration-Resistant Prostate Cancer.

OBJECTIVE: To evaluate the efficacy of enzalutamide (Enz) as fourth- or fifth-line treatment in men with metastasized castration-resistant prostate cancer (mCRPC), by analyzing a retrospective cohort of heavily pretreated patients. METHODS: We evaluated toxicity, overall survival (OS), progression-free survival (PFS) and time to prostate-specific antigen (PSA) progression data from 47 CRPC patients treated with fourth- or fifth-line Enz. RESULTS: All patients were treated with docetaxel and abiraterone acetate and 42 patients (89%) with cabazitaxel. The median age of the patients was 69 years (IQR, 63-73.5), 79% had bone metastases, 55% had lymph node metastases, and 17% had visceral metastases. The median duration of Enz treatment was 12.0 weeks (IQR, 8.3-20.4), and 11 patients (23%) responded to Enz (maximum PSA decline ≥50%). In general, Enz was well tolerated, with the most frequently reported adverse events being fatigue and nausea. The median OS was 40.1 weeks (95% CI, 25.4-61.4), the median PFS was 12.1 weeks (95% CI, 9.9-14.0) and the median time to PSA progression was 15.7 weeks (95% CI, 14.0-28.7). CONCLUSIONS: Analysis of this retrospective cohort suggests that Enz is well tolerated and that there is a 23% response rate in heavily pretreated CRPC patients, which is comparable with third-line treatment outcomes.

Preventing bleeds by treatment: new era for haemophilia changing the paradigm.

INTRODUCTION: Coagulation products have allowed patients with severe haemophilia to lead a normal life. This is, however, only true for patients who received an early diagnosis and could start with primary prophylaxis. The absence of a positive family history for haemophilia, in the majority of children with severe haemophilia, postpones the age that treatment can be started. This makes general awareness of the clinical presentation important and a proper diagnosis a prerequisite for progress. The long delay between joint bleeding and overt arthropathy has been an important factor in the delay of implementation of primary prophylaxis. After the development of guidelines on 'how to treat', implementation of the advised practice is needed. Data collection of current treatment regimens in haemophilia centres will support the further optimization of the care for persons with haemophilia and further optimize treatment guidelines. Episodic ('on demand') therapy as a treatment strategy for severe haemophilia needs reconsideration. CONCLUSION: In an era where clotting factor concentrates are abundant and gene therapy a reality, all patients with severe haemophilia should be offered a strategy of bleeding prevention.

Different impact of factor VIII products on inhibitor development?

Inhibitors are the most serious side effect of haemophilia treatment; they occur in 25-30 % of all patients with severe haemophilia A. Over the last 2 decades, conflicting data on the impact of clotting products have been published. Due to small studies of selected cases, appreciation of the impact of any particular product has been difficult. Moreover, the emphasis on inhibitor testing has led to increased detection of low-titre inhibitors (to >10 %), while the percentage of high-titre inhibitors is still around 20 %. Other non-genetic risk factors, such as dosing and intensive treatment, are able to increase individual inhibitor risk. Early prophylaxis might reduce inhibitor risk. Well-defined large PUP studies including products should be considered. This can only be achieved in collaboration with all stakeholders. In conclusion, while the impact of FVIII products on inhibitor development is large, presently the actual impact of any specific product is unclear.

Assessment of clotting factor concentrates--pivotal studies and long-term requirements.

Assessment of quality in terms of safety and efficacy of clotting factor concentrates (CFCs) is very important for all new therapeutic products. In rare diseases this is often complicated due to small number of trial participants. In hemophilia, an extra complication is the large impact previous treatments have on both the risk on inhibitors and the overall response to bleedings. For new CFCs, safety needs to be evaluated against inhibitor risk whereas efficacy is primarily judged against the most common clinical manifestations of the disease, namely, bleeding into joints and muscles. In this article the challenges are described for hemophilia that recruits patients globally. Recommendations of ISTH are discussed; these propose to substitute the single-arm prelicensure study with a two-stage approach, which considers epidemic and endemic incidence rate, and might increase the feasibility of studying multiple new products in populations with rare disease without compromising the assessment of product safety and efficacy. We also suggest that the annual bleeding rate (ABR) is an unreliable predictor of efficacy. The response to treatment highly depends on the current disease status of every patient participating in a clinical trial. The phenotype of patients with hemophilia is highly influenced by previous treatment history. Patients with severe hemophilia of the same age can demonstrate a different response to treatment.

Correlation between phenotype and genotype in a large unselected cohort of children with severe hemophilia A.

Phenotypic variability is well recognized in severe hemophilia A. A few studies, mainly in adults treated lifelong on demand, suggest that bleeding phenotype correlates with factor VIII gene (F8) mutation type. Because treatment regimens influence outcomes to a large extent, examining bleeding phenotype during the first years of life may be the most suitable way to define this variability. We set out to analyze the very early phenotypic expression of severe hemophilia A in 621 consecutively enrolled, well-characterized previously untreated patients and to correlate this with patients' F8 mutation. Detailed information was collected on bleeds and treatment of the first 75 exposure days or until inhibitor development. F8 mutation type was known for 531 patients; 402 had null mutations and 129 had non-null mutations. Considering only patients who had not started prophylaxis or developed an inhibitor before select bleeding events, we found that patients with null mutations experienced their first bleed and first joint bleed at younger median ages than patients with non-null mutations (9.7 vs 10.9 months and 13.8 vs 16.1 months, respectively). We conclude that F8 mutation type accounts for only a small component of the significant phenotypic variability found among patients with severe hemophilia A.

Intermediate-dose versus high-dose prophylaxis for severe hemophilia: comparing outcome and costs since the 1970s.

Prophylactic treatment in severe hemophilia is very effective but is limited by cost issues. The implementation of 2 different prophylactic regimens in The Netherlands and Sweden since the 1970s may be considered a natural experiment. We compared the costs and outcomes of Dutch intermediate- and Swedish high-dose prophylactic regimens for patients with severe hemophilia (factor VIII/IX < 1 IU/dL) born between 1970 and 1994, using prospective standardized outcome assessment and retrospective collection of cost data. Seventy-eight Dutch and 50 Swedish patients, median age 24 years (range, 14-37 years), were included. Intermediate-dose prophylaxis used less factor concentrate (median: Netherlands, 2100 IU/kg per year [interquartile range (IQR), 1400-2900 IU/kg per year] vs Sweden, 4000 IU/kg per year [IQR, 3000-4900 IU/kg per year]); (P < .01). Clinical outcome was slightly inferior for the intermediate-dose regimen (P < .01) for 5-year bleeding (median, 1.3 [IQR, 0.8-2.7] vs 0 [IQR, 0.0-2.0] joint bleeds/y) and joint health (Haemophilia Joint Health Score >10 of 144 points in 46% vs 11% of participants), although social participation and quality of life were similar. Annual total costs were 66% higher for high-dose prophylaxis (mean, 180 [95% confidence interval, 163 - 196] × US$1000 for Dutch vs 298 [95% confidence interval, 271-325]) × US$1000 for Swedish patients; (P < .01). At group level, the incremental benefits of high-dose prophylaxis appear limited. At the patient level, prophylaxis should be tailored individually, and many patients may do well receiving lower doses of concentrate without compromising safety.